1. Field of the Invention
The present invention relates to a structure of a scale graduation and a vehicle instrument.
2. Description of the Related Art
Among vehicle instruments used for automobiles, some instruments with a graduation ring have been known that achieve improved appearance and visibility of three-dimensional graduations with a simple structure (refer to Japanese Patent Application Laid-open No. 2006-275677, for example). Such an instrument with a graduation ring illustrated in FIG. 5 is assumed an analog engine tachometer used for an automobile. The instrument with a graduation ring includes a graduation ring member 501, a dial plate (a meter dial plate) 503, a red line sheet 505, a light-guiding plate 507, and a substrate 511 including a light source 509. On the graduation ring member 501 having light-guiding property, three-dimensional graduations 513 are disposed in a protruding manner. Between the back surface of the three-dimensional graduations 513 and the light source 509, the red line sheet 505 is disposed in a similar color to the red ink (not illustrated) printed on the three-dimensional graduations 513. With the instrument with the graduation ring, if the print of the red ink is defective, the above-described structure can compensate for the defective print when the light source is on. Accordingly, the instrument with the graduation ring achieves improved appearance and visibility of the three-dimensional graduations 513 with a simple structure.
In recent automobiles, meters with improved appearance have been used by lighting up the light source 509 day and night when the ignition is ON to illuminate the three-dimensional graduations 513 themselves. That is, when the ignition is ON, the graduations are illuminated in a white kind of color. When the ignition is OFF, the graduations are dimmed so that the real image thereof is difficult to see. This operation enhances the effect of representation of the conventional meter by the lighting when the ignition is ON. However, a normal graduation 515 barely appears as a transparent acrylic material. With such a transparent member, the graduation may look cloudy from the view direction due to reflection from the graduation surface, for example. For this reason, when the ignition is OFF, if the graduation 515 look cloudy due to the reflection, the graduation 515 may be recognized as if it illuminates, which reduces the effect of representation of the meter. In particular, if the back surface of the graduation 515 is grained to reduce the luminance of the graduation, the cloudiness is increased. Simply reducing the transmittance of the transparent member will mitigate the cloudiness to some extent. However, it will reduce the lighting effect when the ignition is ON, which leads to insufficient effect of representation, leading to poor appearance.